Pref-1 is highly expressed in presdipocytes, but its transcription decreases during adipocyte differentiation and pref-1 is not detectable in mature adipocytes. In fact, when constitutively expressed by transfection, pref-1 blocks adipose conversion of 3T3-L1 cells. The mechanism for the downregulation of pref-1 is unknown. The long term goal of this proposal is to understand how pref-1 is down-regulated during adipogenesis. The specific aims of the proposed work are: (1) To identify cis-acting sequences within the 5'-flanking region of the pref- 1 gene that mediate its transcriptional down-regulation during adipocyte conversion; (2) To identify cis-acting sequences within the 5'-flanking region of the pref-1 gene that mediate its transcriptional repression by dexamethasone and 15-deoxy-D12,14-prostaglandin J2 in 3T3-L1 fibroblasts;.(3) To characterize the trans-acting factors which bind to the sequences identified in aims 1 and 2. Deletion analysis of the promoter will locate the cis-acting regions involved in the suppression of pref-1. Biochemical mapping techniques will reveal the specific DNA sequences to which regulatory proteins bind.